JP2615651B2 - Biaxially oriented polyester film - Google Patents

Description

The present invention relates to a biaxially oriented polyester film.

[Prior Art] As a biaxially oriented polyester film, a film comprising two or more kinds of particles having different particle diameters in a polyester is known (for example, Japanese Patent Publication No. 61-1316).

[Problems to be Solved by the Invention] However, in the above-mentioned conventional film, as the processing speed of the film increases, for example, a printing process in a packaging application, and a magnetic layer coating / calendering process in a magnetic medium application, the contact speed increases. When the surface of the film is shaved by a roll or the like, there arises a drawback that a trouble occurs in a processing step and a product performance, and there is a problem that a winding property of a pancake or the like cannot be satisfied. An object of the present invention is to solve such problems and to provide a biaxially oriented polyester film having excellent abrasion resistance and winding properties.

[Means for Solving the Problems] The present invention relates to a biaxially oriented polyester film comprising at least two kinds of fine particles A and B in a polyester, wherein the average particle diameter d _{A of the} fine particles _A ≦ fine particles B, the average particle diameter d _B , and the height H _{A of} the film surface projections caused by the fine particles _A > the height H B of the film surface projections caused by the fine particles _B ,
It is a biaxially oriented polyester film characterized by the following.

The polyester in the present invention includes ethylene terephthalate, ethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, and ethylene-phthalate.
At least one type of structural unit selected from 2,6-naphthalate units is the main constituent. However, other components may be copolymerized within a range that does not impair the present invention, preferably within 15 mol%. In addition, in the case of a polyester containing ethylene terephthalate as a main component, scraping resistance and winding properties are further improved, which is particularly desirable.

The fine particles in the present invention are fine particles inert to the polyester, and the type thereof is not particularly limited. Examples of the fine particles A include those having a substantially spherical silicon dioxide-based composition such as colloidal silica. It is preferably exemplified, and the surface may be surface-modified. Examples of the fine particles B include those having a main composition of calcium carbonate such as synthetic calcium carbonate, and the surface thereof may be surface-modified. Furthermore, not only the method of adding fine particles, but also a method of forming surface projections by internally precipitated particles that precipitate fine particles containing calcium, lithium, or phosphorus in the polymerization system during the synthesis of polyester in combination with the addition of fine particles. It can be preferably used. The average particle size of the fine particles in the present invention, the content is not particularly limited, but in order to satisfy the abrasion resistance, winding characteristics, the average particle size is preferably 0.3 to 1.5 μm, more preferably 0.3 to 1.0 μm, and 0.005 added
２2% by weight, more preferably 0.02 to 1% by weight.

The film of the present invention has the above composition as a main component,
As long as the object of the present invention is not impaired, other types of polymers may be blended, or an antioxidant, a heat stabilizer, a lubricant,
Inorganic or organic additives such as ultraviolet absorbers and nucleating agents may be added to the extent that they are usually added. The present invention is a film obtained by biaxially orienting the composition, the refractive index ratio in the thickness direction indicating the degree of the orientation is not particularly limited, when it is in the range of 0.935 to 0.970, abrasion resistance,
This is particularly desirable because the winding characteristics are further improved. The biaxially oriented polyester film of the present invention has on its surface fine projections caused by containing at least two types of fine particles A and B. In general, when fine particles are added to a film-forming polymer and biaxially stretched, it is known that as the particle size of the added fine particles increases, the projection height and surface roughness of the film surface tend to increase. . However, even when fine particles having substantially the same average particle size are added, the projection height and the surface roughness on the film surface do not always match. The present invention relates to fine particles A
Average particle diameter d _A ≦ average particle diameter d _B of fine particles _B , and height H _{A of} film surface protrusions caused by fine particles _A > height H _B of film surface protrusions caused by fine particles B. It is. When d _A ≦ d _B and H _A <H _B , that is, the conventional method of forming low protrusions with small particles and high protrusions with large particles satisfies the winding property and abrasion resistance of the film simultaneously. Can not do it. In other words, if the height of the projections is increased by using fine particles having a large average particle size in order to improve the winding characteristics, the shaving increases, while if the abrasion resistance is to be satisfied, the winding characteristics are not improved. More preferably, d _A
≦ d _B and H _A > H _B +0.02 (μm). Furthermore, d _A
It is particularly preferable that ≦ d _B and H _A > H _B +0.05 (μm), since the abrasion resistance and the winding characteristics are further improved.

The biaxially oriented polyester film of the present invention has a surface space volume (Φ) of 10 ³ to 10 ⁵ , preferably 10 ⁴ to 1.
0 ⁵ , and the refractive index n _{TD in the} film width direction is 1.655 to 1.70.
A value of 0, preferably in the range of 1.675 to 1.700 is particularly desirable because the abrasion resistance and winding characteristics are further improved.

Next, a method for producing the biaxially oriented polyester film of the present invention will be described. The polyester constituting the biaxially oriented polyester film of the present invention can be obtained by directly performing polycondensation via esterification or performing polycondensation via a transesterification reaction. As a method of adding the fine particles to the polymer, a method of adding the particles at the time of polymerization or a method of mixing the polymer particles with the polymer pellets before extrusion can be adopted. further,
The difference ΔTcg between Tcc (cold crystallization temperature) and Tg (glass transition temperature) of the master pellet containing fine particles A is
When it is larger than ΔTcg of the master pellet containing, it is extremely effective to satisfy the conditions of the present invention and to improve the abrasion resistance and the winding property.

As a method for adjusting ΔTcg, there is a method in which an appropriate monomer is copolymerized. As the copolymerizing acid at the time of copolymerization,
Examples include isophthalic acid and aromatic dicarboxylic acids having a metal sulfonate. As the copolymerized diol component,
1,4-cyclohexanedimethanol, neopentyl glycol and the like can be mentioned. In addition, by generating internal precipitation particles and adding inert particles, these particles act as a crystallization accelerator to adjust the ΔTcg of the polymer, and by changing the polymerization time of the polymer, ΔTcg can also be adjusted by adjusting the intrinsic viscosity of.

The following method is effective as a method for generating the internally deposited particles. That is, (1) a process of polycondensation through direct esterification of a predetermined dicarboxylic acid and ethylene glycol, or (2) a polycondensation through a transesterification reaction of dimethyl ester of a predetermined dicarboxylic acid with ethylene glycol. In the process, it is produced by adding at least one of a calcium compound, a magnesium compound, a manganese compound and a lithium compound soluble in glycol, and preferably an acid and / or ester compound of phosphorus. Compounds of calcium, magnesium, manganese, and lithium that can be used here include inorganic acid salts such as halides, nitrates and sulfates, organic acid salts such as acetates, oxalates, and benzoates, hydrides and oxides. Glycol-soluble compounds such as products are most preferably used, but two or more compounds may be used in combination. Further, as the phosphorus compound, one or more of phosphate, phosphorous acid, phosphonic acid, and their esters and partial esters are used.

After sufficiently drying the pellets of the particle-containing polyester obtained by the above method, it is supplied to a melt extruder, at a temperature higher than the temperature at which the pellets are melted, at a temperature lower than the temperature at which the polymer is decomposed, and melt-extruded into a sheet from a slit-shaped die, Cool and solidify to make an unstretched film.

Next, the unstretched film is biaxially stretched and oriented.
As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, and the sequential biaxial stretching method is particularly preferable. As the stretching conditions in this case, a method of stretching 2.7 to 4.0 times in the longitudinal direction and then stretching 3.2 to 4.5 times in the width direction is preferable. In particular, when the stretching ratio in the width direction ≧ the stretching ratio in the longitudinal direction + 0.5 times, it is effective to improve the abrasion resistance and the winding characteristics. The stretching speed is preferably in a relatively low range of 10 ³ to 10 ⁴ % / min, more preferably in order to simultaneously satisfy the above conditions. The stretching temperature is preferably in the range from the glass transition point of the polymer to the cold crystallization temperature. Next, the stretched film is heat-treated, and the heat treatment conditions at that time are a temperature of 180 to 230 ° C, preferably 190 ° C.
A method of heat treatment at a temperature in the range of to 220 ° C. for 0.5 to 60 seconds is effective for improving the properties of the film. Further, it is more preferable that the heat treatment is performed at a constant length in order to improve winding characteristics.

As described above, the biaxially oriented polyester film of the present invention can be obtained.

[Method for Measuring Characteristics and Method for Evaluating Effects] The method for measuring characteristic values and the method for evaluating effects according to the present invention are as follows.

(1) Average Particle Size of Fine Particles The fine particles were dispersed in ethylene glycol or as a water slurry, and the volume average diameter (μm) was measured using a centrifugal sedimentation type particle size distribution analyzer (CAPA500 manufactured by Horiba, Ltd.).

(2) Surface protrusion height Using a two-detector scanning electron microscope (ESM-3200 manufactured by Elionix Inc.) and an energy dispersive X-ray analyzer (SYSTEM-5000 manufactured by Elionix Inc.), the surface protrusions are fine. After determining which of A and B was caused, a height measurement value obtained by scanning with a cross-section measurement device (PMS-1 manufactured by Elionix Inc.) assuming that the height of the smooth surface of the film surface is 0, The image is sent to an image processing device (IBAS2000 manufactured by Carl Zeiss Co., Ltd.) as a gray value of 256 gradations, and a film surface projection image is reconstructed on the image processing device based on the gray value. Next, the maximum gray value of the projection portion binarized in this surface projection image was obtained by converting it to the projection height (μm). Although this measurement was performed on 1 mm ² of the film, the height of the protrusions can be determined by performing the measurement on a film containing only one component of the particles.

(3) Refractive index, refractive index ratio Measured at 20 ° C. and 60% relative humidity using an Abbe refractometer with sodium D line (wavelength 589 nm) as a light source. Note that a sulfur-methylene iodide solution was used as the mounting solution. The refractive index in the thickness direction of the biaxially oriented film (referred to as A) and the refractive index in the thickness direction of the non-oriented (amorphous) film made by quenching into 10 ° C water after melt pressing (B
) Was measured, and A / B was defined as the refractive index ratio in the thickness direction.

(4) Surface space volume (Φ) Using the Kosaka Laboratory high-precision thin film level measuring device ET-10, the tip radius of the stylus is 0.5 μm, the cutoff is 0.08 mm, the measurement length is 1.0 mm, the vertical magnification is 200,000, and the horizontal magnification is 2,000. Measure the surface roughness curve of the film in times. A peak count level is provided every 0.005 μm in parallel above the average line (center line) of the roughness curve,
When there is a point at which the peak count level crosses one or more times between two points at which the curve crosses the average line,
This is defined as one peak, and the number of peaks is determined between the measurement lengths. For each peak count level, the number of peaks is determined, and the number of peaks determined for the n-th peak count level from the average line is defined as PC (n). When the peak count level at which the number of pakes becomes zero for the first time between the measurement lengths is m-th from the average line, the effective space volume Φ is The average value measured 50 times at different locations is used.

(5) Abrasion resistance Press a single blade at an angle of 90 ° on a film obtained by slitting the film into a 1/2 inch wide tape shape, then push in 0.5 mm and push in 20 cm.
Let it run. (Speed: 6.7cm / s, tension: 500g). The adhering height of the powder shaved on one blade was read with a microscope, and the shaved amount (μm) was determined. When the shaving amount is 15 μm or less, the shaving resistance is good, and when the shaving amount exceeds 15 μm, the shaving resistance is poor.

(6) Winding characteristics The film was slit into a width of 300 mm to form a film roll having a length of 5000 m. The end face deviation of the film roll was visually observed. Winding property when no edge displacement is seen and no film vertical wrinkle: Winding property when less than 5, 0.1 mm and no film vertical wrinkling: 4, less than 0.2 mm and slight film wrinkling The case where the film was rolled was determined to be 3, and the case where vertical wrinkles were observed at 0.2 mm or more was determined to be 2;

"If the winding property is 5 or 4, it can be used without practical problems." (7) Glass transition temperature Tg, cold crystallization temperature Tcc, crystallization parameter ΔTcg, melting point Perkin Elmer DSC (Differential Scanning Calorimeter) ) Measured using type II. The measurement conditions for DSC are as follows.
That is, 10 mg of a sample is set in a DSC device, and the
After melting for a minute, quench in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition temperature Tg is detected. The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. The temperature was further raised, and the melting peak temperature was taken as the melting point. Also, the difference between Tcc and Tg (Tcc−
Tg) is defined as a crystallization parameter ΔTcg. The larger ΔTcg is, the harder it is to crystallize.

[Examples] The present invention will be described based on examples and comparative examples.

Example 1 An ethylene glycol slurry containing fine particles was prepared using silica having an average particle size of 0.3 μm and synthetic calcium carbonate having an average particle size of 0.4 μm as the fine particles. The ethylene glycol slurry, 100 parts by weight of dimethyl terephthalate, and 70 parts by weight of ethylene glycol were subjected to a transesterification reaction using 0.1 part by weight of calcium acetate as a catalyst, and the product was subjected to 0.03 part by weight of antimony trioxide, 0.3 parts by weight of lithium and 0.2 parts by weight of trimethyl phosphate were added, and polymerized to obtain a particle master pellet of polyethylene terephthalate having an intrinsic viscosity of 0.615 and each containing 1% by weight of fine particles. Here, ΔTcg of the master pellet containing silica was larger than ΔTcg of the master pellet containing synthetic calcium carbonate. These particle master pellets and polyethylene terephthalate pellets substantially containing no particles were mixed, and the pellets were vacuum-dried at 180 ° C. for 8 hours at a particle content of 0.15% by weight, and then supplied to an extruder. At 280 ° C., discharged from a T-type die into a sheet via a gear pump and a filter, wound the molten sheet around a cooling drum having a surface temperature of 40 ° C., and cooled and solidified to form an unstretched sheet.

This unstretched sheet was guided to a stretching stenter and stretched 3.2 times in the longitudinal direction and 3.7 times in the width direction. Stretching speed is 2 × 10 ³
% / Min in a relatively slow range.
85 ° C. Then, without cooling, the film is directly guided to a heat treatment zone, and is heat-set at 210 ° C. for 3 seconds under tension, followed by 2% in the longitudinal direction and 3% in the width direction at the same temperature.
(Relative to the original length), gradually cooled, cooled to room temperature, and wound up to obtain a biaxially oriented polyester film having a thickness of 15 μm.

Examples 2 to 4 and Comparative Examples 1 to 4 Under the conditions of Example 1, during polymerization, the type of fine particles to be added, the average particle size, the amount added, and the stretching temperature, stretching ratio, heat setting temperature, and heat By varying the degree of relaxation upon fixation, samples with different properties were made. The evaluation results of these films are summarized in Table 1. From Table 1,
When the particle size of the fine particles and the projection height are within the range of the present invention, a film having both the abrasion resistance and the winding characteristics can be obtained, but otherwise, a film having both the abrasion resistance and the winding characteristics cannot be obtained. You can see that.

[Effect of the Invention] The biaxially oriented polyester film thus obtained is
By providing a magnetic layer on one or both sides thereof, it can be used after being processed into various magnetic recording media, for example, video tapes, audio tapes, floppy disks, and the like. The magnetic layer may be formed by applying a magnetic powder together with a binder, or may be formed by thinning a ferromagnetic material by a method such as vacuum deposition, sputtering, ion spraying, or plating. The use of the biaxially oriented polyester film of the present invention is not only for magnetic recording media,
For example, it can be effectively used in applications where abrasion resistance is a problem, such as for graphics, stamping foils, electric insulating materials, dielectrics for capacitors, and packaging.

Claims (1)

(57) [Claims] 1. A biaxially oriented polyester film comprising at least two kinds of fine particles A and B in a polyester, wherein the average particle diameter d _{A of the} fine particles _A ≦ the average particle diameter d _{B of the} fine particles _B , and The height H _{A of} the film surface projections caused by the fine particles _A > the height H B of the film surface projections caused by the fine particles _B ,
A biaxially oriented polyester film, characterized in that: